1. Field of the Invention
This disclosure generally relates to electrical power systems, and more particularly, to power system architectures suitable for commonly controlling DC/AC power converters and DC/DC power converters.
2. Description of the Related Art
An alternating current (AC) electric machine may be coupled to a direct current (DC) system via an AC/DC bi-directional power converter. When the AC electrical machine is operating as a motor, the AC/DC power converter provides power to the AC electric machine by inverting DC power from a DC power source, into AC power.
Alternatively, the AC electric machine may operate as a generator when torque is applied to the machine shaft. For example, when an electric motor is braking, running by inertia, or where an electric vehicle employing the motor is running downhill, the electric motor generates AC electric power. Accordingly, the AC/DC power converter rectifies the AC power generated by the AC electric machine into DC power. The DC power is typically stored in a power storage device, for example, an array of chemical battery cells and/or super- or ultra-capacitors. This mode of operation is sometimes referred to as the regenerative mode.
The DC side of the bi-directional AC/DC power converter is typically coupled to a high voltage (HV) DC bus. Accordingly, power transfers from/to the electric machine, via the AC/DC power converter, are transferred over the HVDC bus to other components of the power system.
An AC/DC system controller is typically employed to control operation of the bi-directional AC/DC power converter such that power, voltage and/or current transmitted over the HVDC bus is regulated (controlled). For example, one of the functions of the AC/DC system controller is to prevent over voltage conditions on the HVDC bus when the AC electric machine is operating in a generator mode. As another example, the AC/DC system controller may control the AC/DC power converter to adjust various operating aspects of the AC electric machine, such as speed and/or torque.
Other components are also employed in the power system, including various loads and DC power sources. Examples of loads include various internal components (such as housekeeping loads, etc.), load drawn by external devices (such as lights, small motors, electronic devices, etc.) or power conditioning devices (such as capacitors, reactors, etc.). Examples of DC power sources include fuel cell systems, DC machines (driven, for example, by a combustion engine), capacitors and batteries. Some types of DC power sources are configured to both provide and store electric energy. Other types of DC power sources are configured to non-renewable fuel energy sources into electric energy.
In some instances, the operating voltage of the load(s) and/or the DC power source(s) is less than the operating voltage of the HVDC bus. Accordingly, coupling between the lower voltage components and the HVDC bus requires a voltage conversion device, the DC/DC power converter. Accordingly, power flow between these load(s) and/or these DC power source(s), and the HVDC, bus is transferred through the DC/DC power converter.
When electric power is supplied to the electric machine (via the above-described AC/DC power converter), power received from these lower voltage DC power source(s) may be stepped up, or boosted, from the relatively lower operating voltage of the DC power source(s) to the relatively higher operating voltage of the HVDC bus by the DC/DC power converter. Conversely, when power is supplied from the electric machine (via the AC/DC power converter), power received over the HVDC bus may be stepped down, or bucked, from the relatively higher operating voltage of the HVDC bus to the relatively lower operating voltage of the DC power source(s) by the DC/DC power converter. Accordingly, DC power sources capable of storing received energy are then able to store the received low voltage DC power for later use.
In addition to transferring power between the DC power source(s) and the HVDC bus, the DC/DC power converter may be operated in a manner which regulates voltage on the HVDC bus and/or the terminals of the DC power source(s). Accordingly, a DC/DC system controller is typically employed to control operation of the DC/DC power converter such that power, voltage and/or current transmitted between the HVDC bus and the DC power source(s) is regulated (controlled).
During the manufacture of devices that employ the above-described components, such as an electric motor vehicle, the AC/DC power converter, the AC/DC system controller, the DC/DC power converter and the DC/DC system controller are typically fabricated or assembled onto separate modular components. These separate modular components are then coupled together using various types of electrical connectors. Such connectors may be interlocking pin/socket devices, wiring harnesses, and/or electrically conductive nuts/bolts or the like. Welding, soldering or the like may also be used to couple connectors of the above-described components. One skilled in the art appreciates the difficulties in, and expense of, coupling the connectors of the above-described components during the manufacturing process. One skilled in the art also appreciates the susceptibility of such connections to wear or other damage, which decreases reliability or the mean time between failure, and shortens the average life-time of the system.